The use of piezoelectric buzzers in personal alert safety systems (PASS) is known. Such buzzers typically comprise a small, thin sheet of material that can be vibrated by a piezoelectric material powered by an alternating current to produce a loud buzzing sound. These buzzers are used, for example, by firefighters who wear the buzzers on their protective gear when entering a fire. When the firefighter is in trouble, such as when the firefighter is knocked to the ground, the buzzer will automatically emit a loud sound enabling others to locate and rescue the firefighter.
Certain disadvantages are known to exist with current PASS-type piezo buzzers. For example, known buzzers are typically made of brass and a soft, low Curie temperature PZT ceramic material. These buzzers are typically engineered to operate when exposed to temperatures of 175° F. for 25 minutes, and to produce a signal at a level of 95 dB or greater in the PASS unit.
In many fire situations, however, a firefighter is faced with temperatures far in excess of 175° F. In such situations, the piezo buzzers previously known may malfunction or even melt, so that the PASS protection is not provided.
A need therefore exists for piezoelectric buzzers capable of operating in a personal alert safety system even when exposed to temperature far in excess of 175° F. The present invention addresses that need.